Every year, a few of the draft's top prospects appear on the confidential list for failed NFL Scouting Combine drug tests.

FOXSports.com has learned the two biggest names for 2010: Georgia Tech running back Jonathan Dwyer and Southern California tight end Anthony McCoy.

Dwyer tested positive in February for amphetamines, but this appears unlikely to hurt his standing as a late first-round/early second-round selection in this week's draft. A source said the positive test was triggered by a prescription medication that Dwyer has NFL clearance to use for a pre-existing condition.

"The NFL knew this going into the Combine," the source said. "Every NFL team is aware of the medication he takes and the confirmation from all the [NFL] doctors involved. Some NFL players take the same medication."

An early-entry junior with a pounding running style, the 5-foot-11, 229-pound Dwyer rushed for 1,385 yards in both the 2008 and 2009 seasons.

McCoy, who is projected as a second-day pick, tested positive for marijuana

A source told FOXSports.com that McCoy's representatives (Priority Sports and Entertainment) revealed the positive test to NFL franchises several weeks ago to give teams time to perform due diligence as part of the scouting process. Such honesty paid dividends in 2005 for Priority client Luis Castillo, who admitted to failing a steroid test at the Combine well before the official results were given to NFL clubs. The defensive end was still selected in the first round by San Diego and hasn't failed a drug test since.

As a senior, McCoy caught 22 passes for 457 yards and one touchdown while struggling with an ankle injury for the second half of the 2009 season. Besides his receiving prowess, the 6-foot-5, 259-pound McCoy is regarded as one of top blocking tight ends in this draft class.